1. Field of the Invention
This invention generally relates to a diffusion plate. More particularly, this invention relates to a diffusion plate for use with a lighting module of a liquid crystal display.
2. Description of the Prior Art
Recently, liquid crystal displays are widely used in many display devices such as televisions, computers, laptops, monitors, cell phones, digital cameras, etc. A backlight module provides the liquid crystal display with a uniform light of sufficient brightness, so that the liquid crystal display can display images normally.
As shown in FIG. 1, a conventional direct lighting-type backlight module 90 includes a light source module 200 and an optical film set 80. The optical film set 80 is a double-layer structure including a first diffusion plate 81 and a second diffusion plate 82, wherein micro-structures are respectively printed on one face of each of the first diffusion plate 81 and the second diffusion plate 82. On the other hand, light emitting diodes (LED) are small in volume and low power consumption. Therefore, light emitting diodes are widely used as the light sources of many electronic devices, including liquid crystal display. However, though a double-layer structure is used, the conventional direct lighting-type backlight module still has insufficient light distribution uniformity. Using double-layer structure or more layers of optical films to maintain certain degree of light distribution uniformity will increase the thickness and the cost of the backlight module. Besides, hundreds of light emitting diodes in general are used in display, such as TV. Therefore, LEDs have a significant contribution to the total cost of the direct lighting-type backlight module.